An embankment dam is a large artificial dam . It is typically created by the placement and compaction of a complex semi- plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes the dam impervious to surface or seepage erosion . Such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance.
30-624: The Nadarivatu Dam , also known as the Korolevu Dam , is a concrete gravity dam on the upper reaches of the Sigatoka River in Nadarivatu District of Nadroga-Navosa Province , Fiji . The primary purpose of the dam is to generate hydroelectric power in a 41.7 megawatts (55,900 hp) run-of-the-river scheme. The Nadarivatu Hydropower Scheme was first identified in 1977 during a hydropower study. Detailed plans for
60-474: A gravity dam is built to support the weight of the dam and all the water, it is quite flexible in that it absorbs a large amount of energy and sends it into the Earth's crust. It needs to be able to absorb the energy from an earthquake because, if the dam were to break, it would send a mass amount of water rushing downstream and destroy everything in its way. Earthquakes are the biggest danger to gravity dams and that
90-432: A problem, as they can scour dam foundations. A disadvantage of gravity dams is that their large concrete structures are susceptible to destabilising uplift pressures relative to the surrounding soil. Uplift pressures can be reduced by internal and foundation drainage systems. During construction, the exothermic curing of concrete can generate large amounts of heat. The poorly-conductive concrete then traps this heat in
120-615: A rock-fill dam is New Melones Dam in California or the Fierza Dam in Albania . A core that is growing in popularity is asphalt concrete . The majority of such dams are built with rock and/or gravel as the primary fill. Almost 100 dams of this design have now been built worldwide since the first such dam was completed in 1962. All asphalt-concrete core dams built so far have an excellent performance record. The type of asphalt used
150-562: A rock-fill dam. The frozen-core dam is a temporary earth dam occasionally used in high latitudes by circulating a coolant through pipes inside the dam to maintain a watertight region of permafrost within it. Tarbela Dam is a large dam on the Indus River in Pakistan , about 50 km (31 mi) northwest of Islamabad . Its height of 485 ft (148 m) above the river bed and 95 sq mi (250 km ) reservoir make it
180-411: A shape like a bank, or hill. Most have a central section or core composed of an impermeable material to stop water from seeping through the dam. The core can be of clay, concrete, or asphalt concrete . This type of dam is a good choice for sites with wide valleys. They can be built on hard rock or softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock. Additionally,
210-403: A shell of locally plentiful material with a watertight clay core. Modern zoned-earth embankments employ filter and drain zones to collect and remove seep water and preserve the integrity of the downstream shell zone. An outdated method of zoned earth dam construction used a hydraulic fill to produce a watertight core. Rolled-earth dams may also employ a watertight facing or core in the manner of
240-466: Is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation. Gravity dams are designed so that each section of the dam is stable and independent of any other dam section. Gravity dams generally require stiff rock foundations of high bearing strength (slightly weathered to fresh), although in rare cases, they have been built on soil. Stability of
270-548: Is a viscoelastic - plastic material that can adjust to the movements and deformations imposed on the embankment as a whole, and to settlement of the foundation. The flexible properties of the asphalt make such dams especially suited to earthquake regions. For the Moglicë Hydro Power Plant in Albania the Norwegian power company Statkraft built an asphalt-core rock-fill dam. Upon completion in 2018
300-486: Is at hand, transport is minimized, leading to cost savings during construction. Rock-fill dams are resistant to damage from earthquakes . However, inadequate quality control during construction can lead to poor compaction and sand in the embankment which can lead to liquefaction of the rock-fill during an earthquake. Liquefaction potential can be reduced by keeping susceptible material from being saturated, and by providing adequate compaction during construction. An example of
330-463: Is why, every year and after every major earthquake, they must be tested for cracks, durability, and strength. Although gravity dams are expected to last anywhere from 50–150 years, they need to be maintained and regularly replaced. Embankment dam Embankment dams come in two types: the earth-filled dam (also called an earthen dam or terrain dam ) made of compacted earth, and the rock-filled dam . A cross-section of an embankment dam shows
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#1732775618118360-525: The California Gold Rush in the 1860s when miners constructed rock-fill timber-face dams for sluice operations . The timber was later replaced by concrete as the design was applied to irrigation and power schemes. As CFRD designs grew in height during the 1960s, the fill was compacted and the slab's horizontal and vertical joints were replaced with improved vertical joints. In the last few decades, design has become popular. The tallest CFRD in
390-543: The 320 m long, 150 m high and 460 m wide dam is anticipated to be the world's highest of its kind. A concrete-face rock-fill dam (CFRD) is a rock-fill dam with concrete slabs on its upstream face. This design provides the concrete slab as an impervious wall to prevent leakage and also a structure without concern for uplift pressure. In addition, the CFRD design is flexible for topography, faster to construct and less costly than earth-fill dams. The CFRD concept originated during
420-573: The Sigatoka River through a 3,225 metres (10,581 ft) long headrace/ penstock tunnel to a power station along the Ba River to the southwest. The power station contains two 20.85 megawatts (27,960 hp) Pelton turbine -generators. The drop in elevation between the reservoir and the power station affords a gross hydraulic head (water drop) of 335.7 metres (1,101 ft). Download coordinates as: Gravity dam A gravity dam
450-404: The base of the dam than at shallower water levels. Thus the stress level of the dam must be calculated in advance of building to ensure that its break level threshold is not exceeded. Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure . The erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds
480-450: The cost of producing or bringing in concrete would be prohibitive. Rock -fill dams are embankments of compacted free-draining granular earth with an impervious zone. The earth used often contains a high percentage of large particles, hence the term "rock-fill". The impervious zone may be on the upstream face and made of masonry , concrete , plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be inside
510-434: The dam in place and against the hydraulic forces acting to move the dam. Even a small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours. The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As
540-442: The dam primarily arises from the range of normal force angles viably generated by the foundation. Also, the stiff nature of a gravity dam structure endures differential foundation settlement poorly, as it can crack the dam structure. The main advantage to gravity dams over embankments is the scour -resistance of concrete, which protects against damage from minor over-topping flows. Unexpected large over-topping flows are still
570-406: The dam structure for decades, expanding the plastic concrete and leaving it susceptible to cracking while cooling. It is the designer's task to ensure this does not occur. Gravity dams are built by first cutting away a large part of the land in one section of a river, allowing water to fill the space and be stored. Once the land has been cut away, the soil has to be tested to make sure it can support
600-417: The early 21st century. These techniques include concrete overtopping protection systems, timber cribs , sheet-piles , riprap and gabions , Reinforced Earth , minimum energy loss weirs , embankment overflow stepped spillways , and precast concrete block protection systems. All dams are prone to seepage underneath the dam, but embankment dams are prone to seepage through the dam as well; for example,
630-420: The embankment, in which case it is referred to as a "core". In the instances where clay is used as the impervious material, the dam is referred to as a "composite" dam. To prevent internal erosion of clay into the rock fill due to seepage forces, the core is separated using a filter. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. When suitable building material
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#1732775618118660-485: The flow of the water and continue to fracture into smaller and smaller sections of earth or rock until they disintegrate into a thick suspension of earth, rocks and water. Therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be written such that it can contain at least a one-hundred-year flood. A number of embankment dam overtopping protection systems were developed in
690-468: The foundation's support strength: the Westergaard, Eulerian, and Lagrangian approaches. Once the foundation is suitable to build on, construction of the dam can begin. Usually gravity dams are built out of a strong material such as concrete or stone blocks, and are built into a triangular shape to provide the most support. The most common classification of gravity dams is by the materials composing
720-448: The largest earth-filled dam in the world. The principal element of the project is an embankment 9,000 feet (2,700 m) long with a maximum height of 465 feet (142 m). The dam used approximately 200 million cubic yards (152.8 million cu. meters) of fill, which makes it one of the largest man-made structures in the world. Because earthen dams can be constructed from local materials, they can be cost-effective in regions where
750-423: The mass of the dam erodes, the force exerted by the reservoir begins to move the entire structure. The embankment, having almost no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them, eroding and removing even more material as it passes through. In the final stages of failure, the remaining pieces of the embankment would offer almost no resistance to
780-574: The project were developed in 2002 and major construction began in 2009. The power station was commissioned on 7 September 2012 but an inauguration ceremony led by Prime Minister Frank Bainimarama was held a week later on 14 September. Funding and loans for the project was provided by several organizations to include the China Development Bank (US$ 70 Million), Fiji Electricity Authority bonds (US$ 50 million), ADZ Bank (US$ 30 million). The 40 m (130 ft) tall dam diverts water from
810-476: The rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam. Earth-fill dams, also called earthen dams, rolled-earth dams or earth dams, are constructed as a simple embankment of well-compacted earth. A homogeneous rolled-earth dam is entirely constructed of one type of material but may contain a drain layer to collect seep water. A zoned-earth dam has distinct parts or zones of dissimilar material, typically
840-408: The structure: Composite dams are a combination of concrete and embankment dams . Construction materials of composite dams are the same used for concrete and embankment dams. Gravity dams can be classified by plan (shape): Gravity dams can be classified with respect to their structural height: Gravity dams are built to withstand some of the strongest earthquakes . Even though the foundation of
870-407: The weight of the dam and the water. It is important to make sure the soil will not erode over time, which would allow the water to cut a way around or under the dam. Sometimes the soil is sufficient to achieve these goals; however, other times it requires conditioning by adding support rocks which will bolster the weight of the dam and water. There are three different tests that can be done to determine
900-504: The world is the 233 m-tall (764 ft) Shuibuya Dam in China , completed in 2008. The building of a dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley. The stress of the water increases linearly with its depth. Water also pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, and causes greater need for adjustment (flexibility) near
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